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<html lang="zc-CN">
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    <title>Document</title>
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<body>
    
    <script>
        //找出数组中 元素为10的下标，有则打印该下标，没有则打印-1
        let arr=[88,20,10,100,50]
        for(let i=0;i<arr.length;i++) {
            if(arr[i]===10) {
                console.log(i);
            }
            else {
                console.log(-1);
            }
        }
    </script>
</body>
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